Drafting machine



Oct. 5, 1937. c. H. LITTLE 2,095,099

DRAFTING MACHINE Filed Dec. 19, 1955 Sheets-Sheet 1 INVENTOR. CHARLES H- L/TTAE ATTORNEY5 Oct. 5, 1937. c. H. LITTLE DRAFTING MACHINE Filed Dec. 19, 1935 2 Sheets-Sheet 2 FIG. 3

R. m V m 5 M E L A W Z r} 8 Patented Oct. 5, 1937 UNITED STATES PATENT OFFICE '1 Claims.

The present invention relates to drafting machines of the wheel and band type, and more particularly to a guard or means for enclosing or partially enclosing the band or bands thereof, especially that portion of the band adjacent to the protractor.

In the present day machines of the wheel and band type the sharp edges of the bands are ordinarily exposed over a considerable distance and the operator is constantly exposed to the danger of being cut or otherwise injured thereby. This is especially true of that part of the band adjacent to the protractor, which, during operation, is rotated back and forth over the wheel immediately underneath or adjacent to the operators hand. The possibility of the band breaking under the high tension to which it is subject, furth er subjects the operator to the danger of being injured by the flying band if either of the bands employed should break under the considerable tension at which they are operated. In order to keep the bands taut and to prevent the same from slipping on the wheels, it is not uncommon for them to be operated under a tension of one hundred pounds or more and they are stretched accordingly. The back and forth rotation of the bands over the wheels causes crystallization thereof, due to which, or for various other reasons, the band is liable to break at any time causing possible serious injury to the operator.

The object of the present invention is the provision of a drafting machine of the wheel and band type provided with a novel guard or cover for the band adjacent the protractor which will protect the operator from being cut or otherwise injured thereby, together with means for stopping the force of the bands in the event they should break during operation of the machine.

The present invention resides in certain novel details of construction and combinations and arrangements of parts, and further advantages thereof will be apparent to those skilled in the art from the following description of the preferred embodiment thereof, described with reference to the accompanying drawings forming a part of this specification, in which similar reference characters designate corresponding parts throughout the several views, and in which:

Fig. 1 is a plan view of a drafting machine embodying the present invention;

Fig. 2 is a front elevation of the protractor end of the drafting machine shown in Fig. 1;

Fig. 3 is a perspective view of the guard or cover for the band adjacent the protractor;

Figs. 4 and 5 are perspective views of the guards applied to the band forming part of the protractor parallelogram of the drafting machine shown in Fig. 1; and

Figs. 6, 7 and 8 are sectional views of bands of modified construction.

Referring to the drawings, the drafting machine shown therein comprises a parallel motion mechanism or arm provided at one end with a movable anchor A for attachment to a drawing board or table, and at the other end with a protractor assembly or head 13 including rulers l and II, etc. The parallel motion mechanism or arm consists of two parallelograms comprising endless flat flexible steel bands I2 and 13 encircling equal diameter wheels held apart or in spaced relation by adjustable struts C and D, comprising tubular members ll provided with end members i and I6 of any suitable shape, which project over the respective wheels and with respect to which they are rotatably connected.

The protractor assembly B, per se, forms no part of the present invention and a detailed description thereof will not begiven. Sufflce it to say that preferably it is of the type which per- 25 mits rotation of the rulers through 360. The bands I 2 and i3 are preferably unattached to the wheels except for the friction therebetween. This construction allows the elbow of the arm to be thrown to either side of the center line, thereby enabling every part of the board or table to be reached.

As previously stated, the present invention contemplates means for protecting the operator from injury by the band. To this end I have provided a guard, designated generally by the reference character E, which forms a ,completecover for that part or end of the band 13 adjacent the protractor assembly. The guard may be of any desired shape or construction so long as it prevents the hand of the operator from comingin contact with the band or being caught between the wheel and band during the normal operation of the machine. As illustrated, the guard E comprises a sector shaped portion 20 carried by or attached to the right hand end of the member it of the strut D, by a flange 2|, and provided with two channel shaped members or rods 22 and 23 formed integral therewith, projecting towards the left as viewed in the drawings. The outside 50 flanges 25 and 26 of the channel shaped members continue around the edge of the sector shaped portion 20 to form a closed end about the band. The channel shaped members or rods 22 and 23 open downwardly, enclosing the band I3 on three sides, and extend towards the elbow of the machine a suitable distance where they are connected to and supported bythe strut D through the medium of a cross member 21 riveted or otherwise secured to the ends thereof and connected to the strut in any convenient or suitable manner. From the foregoing description of the guard E, it will be apparent that with the present construction it is impossible for the operator to be injured by the band l3 either in the normal operation of the machine or in' the event the same should break.

I have also provided means for preventing the band l2 of the anchor parallelogram from flying, in the event it should break. Two different forms of guards, designated generally by the reference characters F and H, are shown. These guards maybe used together, as shown, or separately, as

will be hereafter more readily apparent. The

guard 1" consists of two channel shaped rods or members 30 and 3| opening downwardly, enclosing opposite sides of the band i2 on three sides, pivotally connected as by rivets 32 to opposite ends of a cross member 33 carried by the strut C. The top and inside flanges of channel shaped rods are preferably cut away intermediate the ends thereof forthe purpose of reducing the weight etc. As illustrated the rods 30 and 3| are connected to the cross member 33 adjacent their upper ends and the construction is such that if the band breaks below the pivot or rivets 32, that is, between the pivot and the elbow of the arm, the movement of.,the free ends of the'band will cause the rods 33 and 3| to pivot and kink or hold the band within the channel thereof. If desired, the ends of the flanges of the rods or members 30 and 3| may be'bent inward, as shown at 34, to assist in kinking and gripping the band upon failure thereof. In the embodiment illustrated the rods 33 and 3| are relatively short and are used in conjunction with the guards H, but the latter guards may be omitted and the rods 30 and 3| extended to enclose any desired proportion of the band l3.

The guards H merely consist of a strip of metal 43 secured to the strut C and having the ends 4| bent in such a manner that they substantially encircle the sides of the band l3. This construction is very simple but effective and any desired number of such guards may be employed. It will also be apparent that the rods or members 22 and 23 of the guard E may be omitted altogether or extend only a short distance from the protractor assembly, and if desired, supplemented by one or more guards similar to the guards F or H. If the I rods or members 22 and 23 are made relatively short, the support for the left hand ends thereof may be omitted.

The possibility of the operator being injured by the sharp edges of the band may be lessened to some extent by either rounding the edges of the band, or by coating or covering the edges thereof or the entire band with a non-metallic substance such as rubber or the like. Fig. 6 shows a band ll having rounded edges, as suggested above, Fig. 7 shows a band 48 having the sides thereof covered or coated with rubber or the like designated by the reference character 41, and lflg.-8 shows an entire band l8 provided with a rubber or non-metallic coating 49. The use of a coating rubber or some such material on the inside of the band also increases the friction between the band and wheels, thereby reducing the tension required to prevent relative rotation therebetween. a 1

While the preferred embodiments of the invention have been illustrated and described, I do not wish to be limited to the particular construction shown, which may be varied within the scope of this invention, and I particularly point out and claim as my invention the following:

l. A drafting machine comprising a parallel motion am, said arm comprising a plurality of wheels, a flexible band operatively connected to said wheels, a center strut operatively connected to said wheels for maintaining the same in spaced relation, and a guard attached to said strut covering at least a portion of said band.

2. A drafting machine comprising a parallel motion arm, said arm comprising a plurality of wheels, a flexible endless band extending about the wheels, a center strut operatively connected to the wheels for maintaining the same in spaced relation, and guard means attached to the'strut g and extending laterally thereof adjacent the band.

3. A drafting machine comprising a parallel motion arm, said am comprisinga plurality of wheels, a flexible endless band operatively connected to said wheels, a strut operatively con-' nected to said wheels for maintaining the same in spaced relation, and a pivoted guard member supported by said strut and extending adjacent to the band.

4. A drafting machine comprising a parallel motion arm, said arm comprising a pair ofwheels, a flexible band operatively connected to said wheels, a center strut operatively connected to said wheels for maintaining the same in spaced relation, a protractor assembly operatively connected to one end of said arm, and a guard carried by said strut covering a portion of said band adjacent said protractor assembly.

5. A drafting machine comprising a parallel motion arm having a section including a plurality of wheels, an endless flexible band extending about said wheels, a strut operatively connected to the wheels for maintaining the same in spaced relation, and a guard carried by said strut and covering the curved portion of the band adjacent one end of the arm section.

6. A drafting machine comprising a parallel motion arm having a section including a plurality of wheels, an endless flexible band extending about said wheels, a strut operatively connected to the wheels for maintaining the same in spaced relation,-and a guard carried by said strut and covering the curved portion of said band adjacent one end of the section and also portions of the straight sections of the band extending from said curved portion. I

7. A drafting machine comprising a parallel motion arm having a section including a plurality of wheels, an endless flexible band having curved portions extending about said wheels, and a strut operatively connected to the wheels for maintaining the-same in spaced relation, said strut having a guard covering the outer side of at least a portion of the curved part of said band. I

CHARLES H. LITTLE. 

